1. Field of the Invention
This invention relates in general to the control of an induction motor apparatus driven from a DC power source through an inverter.
2. Description of the Prior Art
In a variable voltage and variable frequency AC motor drive apparatus the three phase input voltage from either a DC or a rectified AC source is applied to the motor through an inverter including a network of six power switches. A typical power switch is a gate turn off thyristor. If these power switches were ideal in operation and did not have switching time delays, the output voltage waveforms from the inverter as applied to the motor would be substantially the same as theoretical square waveforms. However the switches do have time delays which change the output voltage waveforms. It is difficult to run the motor as desired without the feedback measurement of the voltage out of the inverter and compensation of the output voltage for the dead time switching effects with the use of a motor controller to adjust the synthesis operation to provide the desired output voltage, and such feedback requires additional isolation and signal correction operations.